It is known that an unsaturated carboxylic acid or an unsaturated nitrile can be synthesized by a vapor phase catalytic oxidation or ammoxidation reaction using an alkane as a starting raw material. As the catalyst for the vapor phase catalytic oxidation or ammoxidation reaction, a composite metal oxide containing Mo, V, and Te, or containing Mo, V, and Nb is used. Since the yield of the target unsaturated carboxylic acid or unsaturated nitrile directly relies on the composition of the composite metal oxide, in the past various compositions have been investigated.
On the other hand, it is also known that the carrier on which the composite metal oxide is supported and the physical properties and chemical properties of the whole catalyst have an effect, though not small, on catalyst performance. Accordingly, investigations are progressing on this point too.
Patent Literature 1 describes, as a catalyst for a vapor phase catalytic oxidation reaction or vapor phase catalytic ammoxidation reaction of propane or isobutane, a catalyst which supports a composite metal oxide containing Mo, V, Nb, and B on silica which has a SiO2 content of 20 to 60 mass % based on the total mass of the oxide and the silica.
Patent Literature 2 describes a silica-supported catalyst which is used when producing an unsaturated nitrile by a vapor phase catalytic ammoxidation reaction of propane or isobutane, or used when producing an unsaturated carboxylic acid by a vapor phase catalytic oxidation reaction. The described silica-supported catalyst has a specific metal component composition, silica content, and pore volume.